The purification of waste water is an important part of virtually any modern industrial process. In particular, much effort has been expended in recent years in insuring that the risk of pollution is minimized by treating waste water before it is discharged into rivers and other water-ways. Another important reason for the treatment of waste water is that it enables the water to be re-used in the industrial processes, so forming a closed cycle which is both more efficient and thus more economical. A further economical consideration is that the solid material recovered in the treatment of waste water may, in some instances, be a usable and valuable material in itself.
This invention relates to the treatment of waste water produced in a fiberglass manufacturing process, which enables the water to be recycled through the fiberglass manufacturing process.
There are four major uses for water in a fiberglass manufacturing process. Firstly, cooling water is required for furnaces, compressors and the like. Secondly, water is used to quench the molten glass should the process have to be stopped for any reason. When the molten glass is quenched in this manner it rapidly solidifies and fractures into fragments called cullet. Thirdly, water is used to carry away waste glass fibers and binder from the area in which the fiberglass is formed. Fourthly, water is used in a scrubber system to reduce air pollution. The water used in these four areas makes up the majority of the waste water of a fiberglass manufacturing process.
The principal contaminants carried by the waste water used in the above procedures are glass fiber particles and waste binder. The binder is normally a urea-formaldehyde resin or phenol-formaldehyde resin, and gives rise to dissolved and suspended solids in the waste water. The resin is formed by reacting urea or phenol with formaldehyde, and heating the mixture to give varying degrees of polymerization. The dissolved solid contamination in the water results from resin solids with a low degree of polymerization which are water-soluble. Such resin solids, if recovered, would be reusable in the process. The suspended solid contamination comprises glass particles and those resin solids which have been polymerized by the heat in the forming process to such an extent that they are water-insoluble.
It is the presence of the organic material in the waste water which gives rise to the high chemical oxygen demand (C.O.D.), and a reduction of the organic material leads to a reduction in C.O.D. The reduction of C.O.D. is very important if the treated waste water is to be discharged into a river, since a high C.O.D. would mean that the waste water consumed the oxygen in the river water which supports the plant and animal life therein.
If the waste water were not treated, it would be possible to recycle it to a very limited extent until the level of contamination rose to an unacceptable level. However, the solids content rapidly builds up to an un-acceptable level -- even as high as 7 to 8% -- and it is then necessary to shut down the plant and clean out the water system. If this is not done the efficiency of the process suffers badly, and in particular the spray system, by which water is sprayed onto the fiberglass to remove waste materials, is reduced in efficiency, since a high concentration of resin or fiberglass particles blocks the spray nozzles.
Accordingly, it is highly desirable to treat the waste water in order to maintain the contamination at an acceptable level for as long as possible, so as to maximize the time between stoppages, or eliminate stoppages completely. In the past a number of chemical treatments have been utilized for such a purpose, although none have been entirely safisfactory in treating the waste water from a fiberglass manufacturing process.
One treatment that has been employed to a significant extent uses alum as a coagulating agent to promote precipitation of solid contamination. However, the use of this compound did not give entirely satisfactory results, and also suffered from the additional problem that it introduced aluminum ion into the water which is not desirable because aluminum shows some toxicity to plants.
In another process for the recycling of waste water from a fiberglass manufacturing plant, barium hydroxide is added to the waste water to improve its detergent properties, and a part of the water treated with barium hydroxide is drawn off and used in the formation of binder for the process. This draw-off portion of the waste water is acidified with a weak acid such as ammonium sulfate to reduce the alkalinity of the water to about pH 7 before it is employed in binder make-up. However, this process allows the dissolved ions in the bulk of the waste water to rise to a high level, and it should be pointed out that barium ion is also an undesirable constituent of the treated waste water because of its high toxicity.
It is an object of the invention, therefore, to provide an effective treatment for waste water from a fiberglass manufacturing process to reduce its solids content without introducing toxic ions into the water.
It is also an object of the invention to reduce the chemical oxygen demand of the waste water from a fiberglass manufacturing process.